Angle-resolved photoemission study and first principles calculation of the electronic structure of GaTe

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The electronic band structure of GaTe has been calculated by numerical atomic orbitals density-functional theory, in the local density approximation. In addition, the valence-band dispersion along various directions of the GaTe Brillouin zone has been determined experimentally by angle-resolved photoelectron spectroscopy. Along these directions, the calculated valence-band structure is in good concordance with the valence-band dispersion obtained by these measurements. It has been established that GaTe is a direct-gap semiconductor with the band gap located at the Z point, that is, at Brillouin zone border in the direction perpendicular to the layers. The valence-band maximum shows a marked p-like behavior, with a pronounced anion contribution. The conduction band minimum arises from states with a comparable s- p-cation and p-anion orbital contribution. Spin-orbit interaction appears to specially alter dispersion and binding energy of states of the topmost valence bands lying at Γ. By spin-orbit, it is favored hybridization of the topmost pz-valence band with deeper and flatter pₓ-py bands and the valence-band minimum at Γ is raised towards the Fermi level since it appears to be determined by the shifted up pₓ-py bands.